The below-identified Patent documents 1 and 2 disclose pressed pulleys which are used in tensioners for engine accessory driving belts or timing belts, of automotive engines, or as idler pulleys for adjusting belt winding angles.
The pressed pulley disclosed in Patent document 1 includes a belt winding portion as an outer tubular portion around which a belt is wound, a press-fitting portion as an inner tubular portion provided inside the belt winding portion, and a side plate portion through which the belt winding portion and the press-fitting portion are coupled together. The pressed pulley is formed by pressing a steel sheet such that the winding portion and the press-fitting portion are bent in the same axial direction.
A press-fitting portion-side corner portion provided at the integral portion between the press-fitting portion and the side plate portion comprises a plurality of circular arcs having different radii of curvature such that the press-fitting portion and the arc adjacent to the press-fitting portion, the adjacent arcs, and the side plate portion and the arc adjacent to the side plate portion are connected together by tangential lines, and such that the press-fitting portion side corner portion has a larger radius of curvature. With this arrangement, it is possible to reduce stress generated in the press-fitting portion-side corner portion, thereby preventing breakage of the pulley.
On the other hand, the pressed pulley disclosed in Patent document 2 includes, as with the pressed pulley of Patent document 1, a belt winding portion as an outer tubular portion, an inner tubular portion provided inside of the outer tubular portion, and an annular flange portion (corresponding to the side plate of Patent document 1) through which the inner tubular portion and the belt winding portion are integrally coupled together. The inner tubular portion and the flange portion define a corner portion having an increased thickness so as to prevent fatigue breakage of the pulley at or around its portion when maximum stress is applied.